A phosphorus effusion cell for molecular beam epitaxy is disclosed. It consists of a vessel in which, by sublimation of red phosphorus, the vapor of this element is produced, the vessel being closed by means of a vacuum tight valve which regulates its flow. In the vessel, there are two zones having different temperatures, one of sublimation of red phosphorus and another of condensation and re-evaporation of white phosphorus, both zones being thermally insulated by means of reflecting screens which prevent the temperature of the heating resistance from having to reach temperatures above 350 DEG C. The valve, intermittent closing of which regulates the effusion of phosphorus vapor, is at a temperature slightly above that of the thermostated zone of condensation/re-evaporation of the white phosphorus. It finds applicable in the manufacture of semiconducting structures.